Process-oriented clamping of a diaphragm assembly

ABSTRACT

The invention relates to a diaphragm pump comprising a diaphragm assembly and a diaphragm retrieval device comprising a tensile bar, said diaphragm assembly comprising a diaphragm and a diaphragm retaining device which secures said diaphragm, wherein the diaphragm assembly and the tensile bar are force-fittingly interconnected by means of a magnetic force of adhesion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a National Stage Application under 35 U.S.C. § 371 of PCT/DE2019/100186, filed on Feb. 28, 2019, which claims priority to German Patent Application having serial number 10 2018 109 933.9, filed on Apr. 25, 2018, which is incorporated by reference herein.

BACKGROUND OF THE INVENTION Field of the Invention

Embodiments of the present invention relate to a diaphragm pack for a diaphragm pump.

Description of the Related Art

Diaphragm pumps have a delivery chamber, which has a suction connector and a pressure connector, and a working chamber, which is separated from the delivery chamber by a diaphragm. In order to deliver a medium, the diaphragm is moved back and forth in an oscillating manner between a first position and a second position in that the working chamber is filled with a hydraulic fluid which is subjected to an oscillating pressure. Here, the two positions of the diaphragm are normally referred to as the pressure stroke position and as the suction stroke position.

Hydraulically operated diaphragm pumps are preferably used in the delivery of delivery fluids at high pressures, since, as a result of the hydraulic fluid, uniform loading of the diaphragm is realized and the latter consequently has a long service life.

For the operation of diaphragm pumps, the quality of the diaphragm and the exact processing thereof are of the utmost importance here. For producing the diaphragm, firstly here a, normally PTFE (polytetrafluoroethylene)-based, preform is made available and provided with a central locking bore, which is also referred to as the center.

If a high-quality diaphragm is made available, this has to be integrated into a diaphragm pack in order to be usable in a diaphragm pump. Here too, the utmost precision is required. In this case, the diaphragm is normally braced between two core components of the diaphragm core and centered by means of a guide element and the center.

A problem here is that the PTFE layer of the diaphragm has a coefficient of thermal expansion which differs greatly from those of the further elements of the diaphragm pack, and at the same time its thermal expansion is nonlinear. The reason for this is recrystallization at approximately 23° C. This gives rise to an increase in volume of approximately 6% between 10° C. and 40° C. for the PTFE layer, which leads to problems specifically in the bracing.

In practice, temperature differences of up to 60° C., with correspondingly great changes in volume of the PTFE layers, prevail between the installation and the operation of diaphragm packs. It should be noted here that the core bracing changes not linearly but proportionally, with a relatively large factor of for example 3 or more, with the change in volume.

Several methods are therefore known in the prior art for such bracing. These are based on either the diaphragm packs being produced by means of a press-fit connection under very high forces or the bracing being provided by screwing together the two core components.

A press-fit connection has the disadvantage that the setting and checking of the bracing is highly complex, and moreover such diaphragm packs have only limited pressure resistance.

The diaphragm packs produced by means of screwing also have disadvantages. In order to ensure the bracing, the screw generally has to be tightened to a fixed stop. In this case, the bracing process is normally to be completed in a specific time since the provided screw-locking agent, for example an adhesive, cures. Since, moreover, large forces are required for bracing, a spacing between flats for engagement of a tool is normally provided at the core components, which at a later stage constitutes a risk of deposition in the dosing chamber.

Consequently, there are known two methods which in each case have in particular the disadvantage that, without changing the diaphragm pack elements to be assembled and braced, it is always the case that only a specific degree of bracing can be provided. Moreover, the installation itself is complex and has little flexibility and has to take place within a time which is predefined by the installation methods (press-fit connection, adhesive). Owing to the described different coefficients of thermal expansion of the diaphragm and the core components, it is specifically the case that a decrease in the PTFE volume of the diaphragm is disadvantageous, since the sealing action in the clamping zone of the core is reduced. Here, there is the additional difficulty that, as already explained, with the press-fit connection, the flow behavior of the diaphragm cannot be influenced directly, but rather is determined by the times predefined for the respective methods.

In order to prevent failure of the diaphragm, the core must consequently always be braced so firmly during installation that, under all the process conditions, a sufficient degree of bracing is maintained. This is complex and, owing to the large forces which are necessary for bracing, is not always possible to a sufficient degree.

SUMMARY

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. It is emphasized that the figures are not necessarily to scale and certain features and certain views of the figures can be shown exaggerated in scale or in schematic for clarity and/or conciseness.

FIG. 1 shows a perspective view of an embodiment of a diaphragm pack according to the invention in the non-assembled state.

FIG. 2 shows a perspective view of an embodiment of a diaphragm pack according to the invention with a diaphragm arranged on the diaphragm-holding element.

FIG. 3 shows a perspective view of the embodiment from FIGS. 1 and 2 of a diaphragm pack according to the invention in the assembled state.

Further features and advantages of the invention emerge from the following description, in which exemplary embodiments of the invention will be discussed by way of example on the basis of schematic drawings, without restricting the invention as a result.

DETAILED DESCRIPTION

The object of the present invention is therefore to overcome the disadvantages of the prior art, and in particular to provide a diaphragm pack which, without variations to the components, allows simple and secure bracing with a settable degree of bracing for different process conditions, wherein the installation process is additionally configured to be simplified and variable in terms of time.

The object is achieved by a diaphragm pack for a diaphragm pump that comprises at least one diaphragm-holding element, which has a first connection section, a diaphragm, which has at least one diaphragm layer, and a clamping element, which has a second connection section, wherein the diaphragm is sectionally arranged between the connection sections of the diaphragm-holding element and clamping element, wherein a guide element projecting from the diaphragm-holding element is comprised, and the clamping element is connected in a threadless manner to the guide element of the diaphragm-holding element by means of a fastening means, wherein the diaphragm is braced between the connection sections by a clamping force X, and wherein the clamping force X is not set by the fastening means.

The present invention is based here on the surprising finding that a diaphragm pack allows optimal bracing of the diaphragm when the bracing of the diaphragm is separate from the locking of the diaphragm pack in the braced position.

According to the methods known from the prior art, the bracing and locking are always realized in a single step, whether this be in the known press-fit connection or in the known methods using clamping screws.

According to the invention, the disadvantages of these solutions are completely eliminated; rather, it is possible for the first time for a diaphragm pack to be set different degrees of bracing and without mechanical changes to said diaphragm pack.

For this purpose, the diaphragm is sectionally brought into abutment with the first connection section of the diaphragm-holding element, then the clamping element, under the action of force, is brought into sectional abutment with the diaphragm, and finally, after bracing has been realized, the clamping element is firmly connected to the guide element by the fastening means and fixed.

For this purpose, according to the invention, it is advantageous for the clamping element to be connected to the diaphragm-holding element by a threadless fastening means, since, as a result of this threadless connection, free positioning of the clamping element relative to the diaphragm-holding element is possible.

It is, as explained, consequently possible for the clamping force X provided by the diaphragm-holding element and the clamping element to be decoupled from the fastening means, so that said clamping force is not set by the fastening means.

Here, it is unimportant which degree of bracing is set. The clamping force X is freely selectable. It is possible for example to also resort to external auxiliary aids, such as hydraulic presses, to allow provision of particularly large installation forces. Here, it is particularly advantageous for the bracing to be able to be set according to different process conditions in each case directly and without modifications to the individual elements of the diaphragm pack, wherein the particular coefficient of thermal expansion of the PTFE, layers can be taken fully into account.

Furthermore, there is no temporal limitation on the duration of the bracing process, since it is not necessary to bear in mind a curing speed of a screw-securing agent. The flow process of the diaphragm that is required for sealing can thus be further optimized and, according to requirement, carried out slowly or with breaks. In this way, the operational reliability of the diaphragm pack can be further increased.

It is also provided according to the invention that the installation of the diaphragm pack is realized in a fully or partly automatic manner. This is particularly advantageous because sources of human error, such as excessive or insufficient tightening of the clamping screws, according to the prior art are avoided. In addition, it is advantageous that the clamping element can have a surface which is as smooth as possible, so that, by contrast to the clamping screws up to now, no positions of engagement are present for impurities or deposits to accumulate.

According to one embodiment of the invention, it may be provided here that the first and/or the second connection section comprise(s) depressions which are arranged in particular in the form of concentric circles about the center point of the diaphragm-holding element and/or of the clamping element.

Such depressions increase the mechanical resistance of the connection of the diaphragm and the diaphragm-holding element or the clamping element and, moreover, can serve for improved sealing.

It may furthermore be provided that the diaphragm and the clamping element each comprise an, in particular central, cutout such that the diaphragm and the clamping element are plugged onto the guide element and are guided by the latter in two movement axes.

Such a formation of a guide element has the advantage that, in a similar manner to that in the case of a clamping screw, centering of the diaphragm and the clamping element in relation to the diaphragm-holding element can be ensured.

Here, it may be particularly advantageous for the guide element to form a receiving collar for centrally receiving the clamping element.

By way of such a receiving collar, the clamping element can be brought precisely into the desired abutment with respect to the guide element.

It may furthermore be provided that the clamping element is connected to the guide element by means of welding, adhesive bonding, crimping and/or pinning.

By contrast to the clamping screws known from the prior art, welding, adhesive bonding, crimping and/or pinning of the clamping element and the guide element make(s) it possible for a predefinedly braced position to be maintained without the fixing of the two elements having an influence on the degree of bracing. Here, the welding, adhesive bonding, crimping and/or pinning evidently form(s) the fastening means according to the invention.

Here, it may be particularly advantageous for the clamping element, in the connected state, to form together with the guide element of the diaphragm-holding element a groove for a weld seam, wherein the groove is formed in particular on that side of the clamping element which faces away from the diaphragm.

This formation of a weld seam has proven to be advantageous for large forces, since in this way a stable and secure connection between the clamping element and the guide element is achieved.

According to one embodiment of the present invention, it may also be advantageous for the firm connection of the guide element and the clamping element to be realized exclusively in a region spaced apart by at least the thickness of the diaphragm in the fixed state from the connection section for the guide element-side end of the diaphragm-holding element.

Irrespective of the spacing by the thickness of the diaphragm in the fixed state, the firm connection of the clamping element and the guide element in the context of the present invention differs from the prior art in that the connection is always realized in the region of the clamping element arranged on the guide element and not in the region of the diaphragm-holding element, as would be the case with a clamping screw screwed into said diaphragm-holding element.

However, it has proven to be particularly advantageous for a connection to be realized between the clamping element and the guide element at the end opposite the second connection section, since a weld seam can be produced there particularly easily and reliably. In the case of a crimp, adhesion or pins for producing the connection, it may be particularly advantageous for this/these to be arranged spaced apart at least by the diaphragm thickness in the compressed state from the second connection region, so that the diaphragm does not come into contact with the connection elements.

The invention also provides a method for producing a diaphragm pack, in particular a diaphragm pack according to the invention, comprising the following steps, in particular in this sequence:

-   -   a) providing a diaphragm-holding element which has a first         connection section and has a guide element projecting from the         first connection section;     -   b) providing a diaphragm which has at least one diaphragm layer         and has a cutout corresponding to the guide element;     -   c) plugging the diaphragm onto the guide element, and         sectionally bringing the diaphragm into abutment with the first         connection section;     -   d) providing a clamping element which has a cutout corresponding         to the guide element, and plugging the clamping element onto the         guide element, and then bringing said clamping element into         abutment with the diaphragm;     -   e) subjecting the diaphragm-holding element, the diaphragm and         the clamping element to a force for generating bracing of the         diaphragm pack by a clamping force X; and     -   f) subsequently fixing the diaphragm-holding element, the         diaphragm and the clamping element by firmly connecting the         clamping element to the guide element in the braced state.

It is also clear from the method according to the invention that the invention is based on the separation of bracing and fixing.

It may be provided here that the force provided in step e) and the bracing of the diaphragm that results therefrom are matched to the desired process conditions for the use of the diaphragm.

Finally, the invention provides a use of a diaphragm pack according to the invention in a diaphragm pump, wherein the bracing of the diaphragm pack is predetermined by the process conditions for the diaphragm pump.

FIG. 1 shows by way of example an embodiment of a diaphragm pack 1 according to the invention for a diaphragm pump (not shown). Here, FIG. 1 shows the individual components of the diaphragm pack 1 in the not yet assembled state. FIGS. 2 and 3 show the subsequent assembly steps.

The diaphragm pack 1 comprises a diaphragm-holding element 3, having a first connection section, and a clamping element 5. A three-layer diaphragm 7 is arranged between the diaphragm-holding element 3 and the clamping element 5.

The diaphragm-holding element 3 comprises here a projecting guide element such that the diaphragm 7 and the clamping element 5 can be plugged onto the guide element and are guided by the latter in two movement axes.

Here, it can clearly be seen that, in this exemplary embodiment, the guide element forms a receiving collar for centrally receiving the clamping element.

It can also be seen that the first and/or the second connection section comprise(s) depressions which are arranged in the form of concentric circles 9 about the center point of the diaphragm-holding element 3 and of the clamping element 5.

Said depressions increase the mechanical resistance of the connection of the diaphragm 7 and the diaphragm-holding element 3 or the clamping element 5 and, moreover, can serve for improved sealing.

According to the present embodiment, the clamping element 5 is connected to the guide element of the diaphragm-holding element 3 by means of welding, such that a weld seam 11 forms the fastening means.

Here, the weld seam forms a threadless connection between the diaphragm-holding element 3 and the clamping element 5. It can be clearly seen here that the clamping element 5, in the connected state, forms together with the guide element of the diaphragm-holding element 3 a groove for the weld seam, wherein the groove is formed on that side of the clamping element 5 which faces away from the diaphragm 7.

With reference to FIGS. 1 to 3, it consequently becomes clear that, for producing a diaphragm pack 1 according to the invention, first of all the diaphragm 7 is mounted onto the projecting guide element of the diaphragm-holding element 3 and is brought into abutment therewith. Then, the clamping element 5 is plugged onto the guide element, and the diaphragm-holding element 3, the diaphragm 7 and the clamping element 5 are subjected to a force for generating bracing of the diaphragm pack by a clamping force X. Subsequently, the diaphragm pack 1 is fixed by the fastening element in the form of a weld seam 11.

It is thus clearly shown that the bracing of the diaphragm 7 is separate from the locking of the diaphragm pack 1 in the braced position, and so any desired clamping forces X are settable without changes to the structure of the diaphragm pack 1 having to be made.

In the foregoing discussion and in the claims that follow, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to.” The phrase “consisting essentially of” means that the described/claimed composition does not include any other components that will materially alter its properties by any more than 5% of that property, and in any case does not include any other component to a level greater than 3 mass %. The term “or” is intended to encompass both exclusive and inclusive cases, i.e., “A or B” is intended to be synonymous with “at least one of A and B,” unless otherwise expressly specified herein. The indefinite articles “a” and “an” refer to both singular forms (i.e., “one”) and plural referents (i.e., one or more) unless the context clearly dictates otherwise.

The features of the invention that are disclosed in the above description, in the claims and in the drawings may be essential both individually and in any desired combination for the realization of the invention in its various embodiments. 

1. A diaphragm pack for a diaphragm pump, comprising: at least one diaphragm-holding element having a first connection section, a diaphragm having at least one diaphragm layer, a clamping element having a second connection section, wherein the diaphragm is sectionally arranged between the connection sections of the diaphragm-holding element and the clamping element, a guide element projecting from the diaphragm-holding element, and. a fastening means for connecting the clamping element in a threadless manner to the guide element of the diaphragm-holding element, wherein the diaphragm is braced between the connection sections by a clamping force, and wherein the clamping force is not set by the fastening means.
 2. The diaphragm pack of claim 1, wherein the first connection section or the second connection section comprises depressions arranged in the form of concentric circles about a center point of the diaphragm-holding element or of the clamping element.
 3. The diaphragm pack of claim 1, wherein at least one diaphragm layer of the diaphragm is produced from a polytetrafluoroethylene-based material.
 4. The diaphragm pack of claim 1, wherein the diaphragm and the clamping element each comprise a cutout such that the diaphragm and the clamping element are plugged onto the guide element and are guided by the latter in two movement axes.
 5. The diaphragm pack of claim 1, wherein the guide element forms a receiving collar for receiving the clamping element.
 6. The diaphragm pack of claim 1, wherein the clamping element is connected to the guide element by welding, adhesive bonding, crimping and/or pinning.
 7. The diaphragm pack of claim 6, wherein the clamping element, in the connected state, forms together with the guide element of the diaphragm-holding element a groove for a weld seam, wherein the groove is formed on a side of the clamping element that faces away from the diaphragm.
 8. The diaphragm pack of claim 1, wherein the guide element is connected to the clamping element in a region spaced apart by at least the thickness of the diaphragm in the fixed state from the connection section for the guide element-side end of the diaphragm-holding element.
 9. A method for producing a diaphragm pack, comprising: a) providing a diaphragm-holding element having a first connection section and a guide element projecting from the first connection section; b) providing a diaphragm having at least one diaphragm layer and a cutout corresponding to the guide element; c) plugging the diaphragm onto the guide element to locate the diaphragm into abutment with the first connection section; d) providing a clamping element having a cutout corresponding to the guide element, and plugging the clamping element onto the guide element, and then locating the clamping element into abutment with the diaphragm; e) fixing the diaphragm-holding element, the diaphragm and the clamping element by connecting the clamping element to the guide element to provide the diaphragm pack.
 10. The method of claim 9, wherein a clamp force used to connect the clamping element to the guide element is matched to the desired process conditions for the use of the diaphragm pack.
 11. The use of a diaphragm pack of claim 8 in a diaphragm pump, wherein a clamp force used to connect the clamping element to the guide element is predetermined by the process conditions for the diaphragm pump.
 12. The diaphragm pack of claim 1, wherein the first connection section and the second connection section each comprises a plurality of depressions arranged in the form of concentric circles about a center point of the diaphragm-holding element or the clamping element.
 13. The diaphragm pack of claim 2, wherein at least one diaphragm layer of the diaphragm is produced from a polytetrafluoroethylene-based material.
 14. The diaphragm pack of claim 12, wherein at least one diaphragm layer of the diaphragm is produced from a polytetrafluoroethylene-based material.
 15. The diaphragm pack of claim 12, wherein the diaphragm and the clamping element each comprise a cutout such that the diaphragm and the clamping element are plugged onto the guide element.
 16. The diaphragm pack of claim 15, wherein the guide element forms a receiving collar for receiving the clamping element.
 17. The diaphragm pack of claim 15, wherein the clamping element is connected to the guide element by welding, adhesive bonding, crimping and/or pinning.
 18. The diaphragm pack of claim 15, wherein the clamping element, in the connected state, forms together with the guide element of the diaphragm-holding element a groove for a weld seam, wherein the groove is formed on a side of the clamping element that faces away from the diaphragm.
 19. The diaphragm pack of claim 18, wherein the guide element is connected to the clamping element in a region spaced apart by at least the thickness of the diaphragm in the fixed state from the connection section for the guide element-side end of the diaphragm-holding element. 